Write-once read-many compliant data storage cluster

ABSTRACT

Methods and systems for improving the performance of a write-once read-many (WORM) compliant data storage cluster in which a set of data (e.g., one or more electronic files) stored within the data storage cluster may be made immutable for a data retention time period are described. The data storage cluster may determine whether to lock the set of data to satisfy WORM compliance using a combination of software-based and hardware-based techniques depending on the required data retention time, the size of the set of data to be locked, the cost to move the set of data to WORM compliant hardware storage, and the amount of available disk space corresponding with WORM compliant hardware storage located within data storage nodes of the data storage cluster. Over time, the data storage cluster may repurpose data storage resources within the data storage cluster in order to satisfy WORM compliance.

BACKGROUND

Virtualization allows virtual hardware to be created and decoupled from the underlying physical hardware. For example, a hypervisor running on a host machine or server may be used to create one or more virtual machines that may each run the same operating system or different operating systems (e.g., a first virtual machine may run a Windows® operating system and a second virtual machine may run a Unix-like operating system such as OS X®). A virtual machine may comprise a software implementation of a physical machine. The virtual machine may include one or more virtual hardware devices, such as a virtual processor, a virtual memory, a virtual disk, or a virtual network interface card. The virtual machine may load and execute an operating system and applications from the virtual memory. The operating system and applications executed by the virtual machine may be stored using the virtual disk. The virtual machine may be stored (e.g., using a datastore comprising one or more physical storage devices) as a set of files including a virtual disk file for storing the contents of the virtual disk and a virtual machine configuration file for storing configuration settings for the virtual machine. The configuration settings may include the number of virtual processors (e.g., four virtual CPUs), the size of a virtual memory, and the size of a virtual disk (e.g., a 2 TB virtual disk) for the virtual machine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A depicts one embodiment of a networked computing environment.

FIG. 1B depicts one embodiment of a server.

FIG. 1C depicts one embodiment of a storage appliance.

FIG. 1D depicts one embodiment of a portion of an integrated data management and storage system that includes a plurality of nodes in communication with each other and one or more storage devices.

FIGS. 2A-2K depict various embodiments of sets of files and data structures associated with managing and storing snapshots of virtual machines.

FIG. 3A is a flowchart describing one embodiment of a process for managing and storing virtual machine snapshots using a data storage system.

FIG. 3B is a flowchart describing one embodiment of a process for determining the type of snapshot to be stored using a data storage system.

FIG. 3C is a flowchart describing one embodiment of a process for restoring a version of a virtual machine using a data storage system.

FIG. 4A depicts one embodiment of a portion of an integrated data management and storage system.

FIG. 4B depicts another embodiment of the portion of the integrated data management and storage system of FIG. 4A.

FIG. 4C depicts an alternative embodiment of the portion of the integrated data management and storage system of FIG. 4A that includes nodes running one or more virtual machines.

FIG. 5A is a flowchart describing one embodiment of a process for operating a data storage cluster.

FIG. 5B is a flowchart describing another embodiment of a process for operating a data storage cluster.

DETAILED DESCRIPTION

Technology is described for improving the operation of a write-once read-many (WORM) compliant data storage cluster in which a set of data stored within the WORM compliant data storage cluster may be identified and then locked or made immutable for a data retention time period such that the set of data cannot be rewritten, erased, or altered for the data retention time period. The set of data may comprise one or more electronic files. In response to an instruction to lock the set of data for the data retention time period (e.g., for six months or for six years), the data storage cluster comprising a plurality of data storage nodes may satisfy WORM compliance by transferring the set of data to a WORM compliant hardware storage device in communication with the data storage cluster, by writing the set of data to WORM compliant hardware storage located within data storage nodes of the data storage cluster, or by restricting data access permissions (e.g., setting read-only file access permissions) for the set of data stored within the data storage cluster for the data retention time period. In some cases, the data storage cluster may determine whether to lock the set of data or satisfy WORM compliance using a software-based approach and/or a hardware-based approach depending on the required data retention time, the size (e.g., the aggregate file size for the set of data) of the set of data to be locked, the performance loss or monetary cost to move the set of data to WORM compliant hardware storage, and/or the amount of available disk space corresponding with the WORM compliant hardware storage located within data storage nodes of the data storage cluster. In one example, if the set of data to be locked is less than a threshold data size (e.g., is less than 10 MB) and the data retention time is less than a threshold duration (e.g., is less than a week), then only a software-based approach may be utilized to satisfy WORM compliance; however, if a stronger hardware-based lock is required or the data retention time is greater than the threshold duration, then a hardware-based approach may be utilized instead. Over time, the data storage cluster may repurpose compute and storage resources and add or remove WORM compliant data storage nodes that include built-in WORM compliant hardware storage devices in order to satisfy WORM compliance.

Government regulations and corporate internal policies may require the preservation of electronic data for a data retention time period in a non-rewriteable and non-erasable format. As an example, a healthcare company may be required to follow strict records-retention regulations to retain and preserve electronic files for the data retention time period. The electronic files may comprise electronic messages, patient records, and audit information. To satisfy the data retention requirements, the electronic files may be stored using WORM compliant storage, such as a WORM compliant hardware storage device or WORM compliant cloud-based storage. The WORM compliant hardware storage device may comprise a disk drive (e.g., an SSD or HDD), an optical or magnetic storage device, or a non-volatile semiconductor storage device (e.g., a Flash-based semiconductor memory) in which the stored data may not be erased, overwritten, or altered, but may be read or accessed with authorized access to the stored data. In some cases, the WORM compliant hardware storage device may comprise a one-time programmable memory in which once a memory cell associated with a memory address is changed to a programmed state, the memory cell cannot be changed back to its original, unprogrammed state. In some cases, the electronic files may satisfy WORM compliance by removing write attributes for the electronic files or modifying the access permissions (e.g., via the chmod command in a Unix-based system) for the electronic files or a directory containing the electronic files such that the electronic files cannot be altered.

In some embodiments, a WORM compliant data storage cluster may dynamically apply a combination of hardware-based techniques (e.g., writing data to internal to the cluster WORM compliant data storage, writing data to external to the cluster WORM compliant data storage that is located outside of the data storage cluster, or writing data to WORM compliant cloud storage) and software-based techniques (e.g., modifying file access permissions to data stored within the cluster) to satisfy WORM compliance for one or more electronic files based on the required data retention time for the one or more electronic files, the combined disk size or file size for the one or more electronic files, the amount of available disk space remaining on the internal to the cluster WORM compliant data storage, and/or the number of reads that have occurred to the one or more electronic files within the past threshold amount of time (e.g., the number of times that the one or more files or portions thereof have been read within the past week). As read performance may be reduced by storing a frequently accessed electronic file only on WORM compliant data storage, if the electronic file has been read more than a threshold number of reads within the past threshold amount of time, then a copy of the electronic file may be stored on non-WORM compliant data storage located within the data storage cluster. One technical issue with using external to the cluster WORM compliant hardware storage devices is that the amount of time to retrieve data may be significant (e.g., it may take several hours to retrieve the data). One benefit of dynamically applying a combination of hardware-based and software-based techniques to WORM compliance is that the performance of the WORM compliant data storage cluster may be improved while maintaining WORM compliance and operating costs.

An integrated data management and storage system may be configured to manage the automated storage, backup, deduplication, replication, recovery, and archival of data within and across physical and virtual computing environments. The integrated data management and storage system may provide a unified primary and secondary storage system with built-in data management that may be used as both a backup storage system and a “live” primary storage system for primary workloads. In some cases, the integrated data management and storage system may manage the extraction and storage of historical snapshots associated with different point in time versions of virtual machines and/or real machines (e.g., a hardware server, a laptop, a tablet computer, a smartphone, or a mobile computing device) and provide near instantaneous recovery of a backed-up version of a virtual machine, a real machine, or one or more files residing on the virtual machine or the real machine. The integrated data management and storage system may allow backed-up versions of real or virtual machines to be directly mounted or made accessible to primary workloads in order to enable the near instantaneous recovery of the backed-up versions and allow secondary workloads (e.g., workloads for experimental or analytics purposes) to directly use the integrated data management and storage system as a primary storage target to read or modify past versions of data.

The integrated data management and storage system may include a distributed cluster of storage nodes that presents itself as a unified storage system even though numerous storage nodes may be connected together and the number of connected storage nodes may change over time as storage nodes are added to or removed from the cluster. The integrated data management and storage system may utilize a scale-out node based architecture in which a plurality of data storage appliances comprising one or more nodes are in communication with each other via one or more networks. Each storage node may include two or more different types of storage devices and control circuitry configured to store, deduplicate, compress, and/or encrypt data stored using the two or more different types of storage devices. In one example, a storage node may include two solid-state drives (SSDs), three hard disk drives (HDDs), and one or more processors configured to concurrently read data from and/or write data to the storage devices. The integrated data management and storage system may replicate and distribute versioned data, metadata, and task execution across the distributed cluster to increase tolerance to node and disk failures (e.g., snapshots of a virtual machine may be triply mirrored across the cluster). Data management tasks may be assigned and executed across the distributed cluster in a fault tolerant manner based on the location of data within the cluster (e.g., assigning tasks to nodes that store data related to the task) and node resource availability (e.g., assigning tasks to nodes with sufficient compute or memory capacity for the task).

The integrated data management and storage system may apply a data backup and archiving schedule to backed-up real and virtual machines to enforce various backup service level agreements (SLAs), recovery point objectives (RPOs), recovery time objectives (RTOs), data retention requirements, and other data backup, replication, and archival policies across the entire data lifecycle. For example, the data backup and archiving schedule may require that snapshots of a virtual machine are captured and stored every four hours for the past week, every day for the past six months, and every week for the past five years.

As virtualization technologies are adopted into information technology (IT) infrastructures, there is a growing need for recovery mechanisms to support mission critical application deployment within a virtualized infrastructure. However, a virtualized infrastructure may present a new set of challenges to the traditional methods of data management due to the higher workload consolidation and the need for instant, granular recovery. The benefits of using an integrated data management and storage system include the ability to reduce the amount of data storage required to backup real and virtual machines, the ability to reduce the amount of data storage required to support secondary or non-production workloads, the ability to provide a non-passive storage target in which backup data may be directly accessed and modified, and the ability to quickly restore earlier versions of virtual machines and files stored locally or in the cloud.

FIG. 1A depicts one embodiment of a networked computing environment 100 in which the disclosed technology may be practiced. As depicted, the networked computing environment 100 includes a data center 150, a storage appliance 140, and a computing device 154 in communication with each other via one or more networks 180. The networked computing environment 100 may include a plurality of computing devices interconnected through one or more networks 180. The one or more networks 180 may allow computing devices and/or storage devices to connect to and communicate with other computing devices and/or other storage devices. In some cases, the networked computing environment may include other computing devices and/or other storage devices not shown. The other computing devices may include, for example, a mobile computing device, a non-mobile computing device, a server, a workstation, a laptop computer, a tablet computer, a desktop computer, or an information processing system. The other storage devices may include, for example, a storage area network storage device, a networked-attached storage device, a hard disk drive, a solid-state drive, or a data storage system. The one or more networks 180 may include a cellular network, a mobile network, a wireless network, a wired network, a secure network such as an enterprise private network, an unsecure network such as a wireless open network, a local area network (LAN), a wide area network (WAN), and the Internet.

The data center 150 may include one or more servers, such as server 160, in communication with one or more storage devices, such as storage device 156. The one or more servers may also be in communication with one or more storage appliances, such as storage appliance 170. The server 160, storage device 156, and storage appliance 170 may be in communication with each other via a networking fabric connecting servers and data storage units within the data center to each other. The server 160 may comprise a production hardware server. The storage appliance 170 may include a data management system for backing up virtual machines, real machines, virtual disks, real disks, and/or electronic files within the data center 150. The server 160 may be used to create and manage one or more virtual machines associated with a virtualized infrastructure. The one or more virtual machines may run various applications, such as a database application or a web server. The storage device 156 may include one or more hardware storage devices for storing data, such as a hard disk drive (HDD), a magnetic tape drive, a solid-state drive (SSD), a storage area network (SAN) storage device, or a networked-attached storage (NAS) device. In some cases, a data center, such as data center 150, may include thousands of servers and/or data storage devices in communication with each other. The data storage devices may comprise a tiered data storage infrastructure (or a portion of a tiered data storage infrastructure). The tiered data storage infrastructure may allow for the movement of data across different tiers of a data storage infrastructure between higher-cost, higher-performance storage devices (e.g., solid-state drives and hard disk drives) and relatively lower-cost, lower-performance storage devices (e.g., magnetic tape drives).

A server, such as server 160, may allow a client to download information or files (e.g., executable, text, application, audio, image, or video files) from the server or to perform a search query related to particular information stored on the server. In some cases, a server may act as an application server or a file server. In general, a server may refer to a hardware device that acts as the host in a client-server relationship or a software process that shares a resource with or performs work for one or more clients. One embodiment of server 160 includes a network interface 165, processor 166, memory 167, disk 168, and virtualization manager 169 all in communication with each other. Network interface 165 allows server 160 to connect to one or more networks 180. Network interface 165 may include a wireless network interface and/or a wired network interface. Processor 166 allows server 160 to execute computer readable instructions stored in memory 167 in order to perform processes described herein. Processor 166 may include one or more processing units, such as one or more CPUs and/or one or more GPUs. Memory 167 may comprise one or more types of memory (e.g., RAM, SRAM, DRAM, EEPROM, Flash, etc.). Disk 168 may include a hard disk drive and/or a solid-state drive. Memory 167 and disk 168 may comprise hardware storage devices.

The virtualization manager 169 may manage a virtualized infrastructure and perform management operations associated with the virtualized infrastructure. For example, the virtualization manager 169 may manage the provisioning of virtual machines running within the virtualized infrastructure and provide an interface to computing devices interacting with the virtualized infrastructure. The virtualization manager 169 may also perform various virtual machine related tasks, such as cloning virtual machines, creating new virtual machines, monitoring the state of virtual machines, moving virtual machines between physical hosts for load balancing purposes, and facilitating backups of virtual machines.

One embodiment of storage appliance 170 includes a network interface 175, processor 176, memory 177, and disk 178 all in communication with each other. Network interface 175 allows storage appliance 170 to connect to one or more networks 180. Network interface 175 may include a wireless network interface and/or a wired network interface. Processor 176 allows storage appliance 170 to execute computer readable instructions stored in memory 177 in order to perform processes described herein. Processor 176 may include one or more processing units, such as one or more CPUs and/or one or more GPUs. Memory 177 may comprise one or more types of memory (e.g., RAM, SRAM, DRAM, EEPROM, NOR Flash, NAND Flash, etc.). Disk 178 may include a hard disk drive and/or a solid-state drive. Memory 177 and disk 178 may comprise hardware storage devices.

In one embodiment, the storage appliance 170 may include four machines. Each of the four machines may include a multi-core CPU, 64 GB of RAM, a 400 GB SSD, three 4 TB HDDs, and a network interface controller. In this case, the four machines may be in communication with the one or more networks 180 via the four network interface controllers. The four machines may comprise four nodes of a server cluster. The server cluster may comprise a set of physical machines that are connected together via a network. The server cluster may be used for storing data associated with a plurality of virtual machines, such as backup data associated with different point in time versions of one or more virtual machines.

In another embodiment, the storage appliance 170 may comprise a virtual appliance that comprises four virtual machines. Each of the virtual machines in the virtual appliance may have 64 GB of virtual memory, a 12 TB virtual disk, and a virtual network interface controller. In this case, the four virtual machines may be in communication with the one or more networks 180 via the four virtual network interface controllers. The four virtual machines may comprise four nodes of a virtual cluster.

The networked computing environment 100 may provide a cloud computing environment for one or more computing devices. In one embodiment, the networked computing environment 100 may include a virtualized infrastructure that provides software, data processing, and/or data storage services to end users accessing the services via the networked computing environment. In one example, networked computing environment 100 may provide cloud-based work productivity or business related applications to a computing device, such as computing device 154. The computing device 154 may comprise a mobile computing device or a tablet computer. The storage appliance 140 may comprise a cloud-based data management system for backing up virtual machines and/or files within a virtualized infrastructure, such as virtual machines running on server 160 or files stored on server 160.

In some embodiments, the storage appliance 170 may manage the extraction and storage of virtual machine snapshots associated with different point in time versions of one or more virtual machines running within the data center 150. A snapshot of a virtual machine may correspond with a state of the virtual machine at a particular point in time. In some cases, the snapshot may capture the state of various virtual machine settings and the state of one or more virtual disks for the virtual machine. In response to a restore command from the server 160, the storage appliance 170 may restore a point in time version of a virtual machine or restore point in time versions of one or more files located on the virtual machine and transmit the restored data to the server 160. In response to a mount command from the server 160, the storage appliance 170 may allow a point in time version of a virtual machine to be mounted and allow the server 160 to read and/or modify data associated with the point in time version of the virtual machine. To improve storage density, the storage appliance 170 may deduplicate and compress data associated with different versions of a virtual machine and/or deduplicate and compress data associated with different virtual machines. To improve system performance, the storage appliance 170 may first store virtual machine snapshots received from a virtualized environment in a cache, such as a flash-based cache. The cache may also store popular data or frequently accessed data (e.g., based on a history of virtual machine restorations), incremental files associated with commonly restored virtual machine versions, and current day incremental files or incremental files corresponding with snapshots captured within the past 24 hours.

An incremental file may comprise a forward incremental file or a reverse incremental file. A forward incremental file may include a set of data representing changes that have occurred since an earlier point in time snapshot of a virtual machine. To generate a snapshot of the virtual machine corresponding with a forward incremental file, the forward incremental file may be combined with an earlier point in time snapshot of the virtual machine (e.g., the forward incremental file may be combined with the last full image of the virtual machine that was captured before the forward incremental was captured and any other forward incremental files that were captured subsequent to the last full image and prior to the forward incremental file). A reverse incremental file may include a set of data representing changes from a later point in time snapshot of a virtual machine. To generate a snapshot of the virtual machine corresponding with a reverse incremental file, the reverse incremental file may be combined with a later point in time snapshot of the virtual machine (e.g., the reverse incremental file may be combined with the most recent snapshot of the virtual machine and any other reverse incremental files that were captured prior to the most recent snapshot and subsequent to the reverse incremental file).

The storage appliance 170 may provide a user interface (e.g., a web-based interface or a graphical user interface) that displays virtual machine information, such as identifications of the virtual machines protected and the historical versions or time machine views for each of the virtual machines protected, and allows an end user to search, select, and control virtual machines managed by the storage appliance. A time machine view of a virtual machine may include snapshots of the virtual machine over a plurality of points in time. Each snapshot may comprise the state of the virtual machine at a particular point in time. Each snapshot may correspond with a different version of the virtual machine (e.g., Version 1 of a virtual machine may correspond with the state of the virtual machine at a first point in time and Version 2 of the virtual machine may correspond with the state of the virtual machine at a second point in time subsequent to the first point in time).

FIG. 1B depicts one embodiment of server 160 in FIG. 1A. The server 160 may comprise one server out of a plurality of servers that are networked together within a data center. In one example, the plurality of servers may be positioned within one or more server racks within the data center. As depicted, the server 160 includes hardware-level components and software-level components. The hardware-level components include one or more processors 182, one or more memory 184, and one or more disks 185. The software-level components include a hypervisor 186, a virtualized infrastructure manager 199, and one or more virtual machines, such as virtual machine 198. The hypervisor 186 may comprise a native hypervisor or a hosted hypervisor. The hypervisor 186 may provide a virtual operating platform for running one or more virtual machines, such as virtual machine 198. Virtual machine 198 includes a plurality of virtual hardware devices including a virtual processor 192, a virtual memory 194, and a virtual disk 195. The virtual disk 195 may comprise a file stored within the one or more disks 185. In one example, a virtual machine may include a plurality of virtual disks, with each virtual disk of the plurality of virtual disks associated with a different file stored on the one or more disks 185. Virtual machine 198 may include a guest operating system 196 that runs one or more applications, such as application 197. The virtualized infrastructure manager 199, which may correspond with the virtualization manager 169 in FIG. 1A, may run on a virtual machine or natively on the server 160. The virtualized infrastructure manager 199 may provide a centralized platform for managing a virtualized infrastructure that includes a plurality of virtual machines.

In one embodiment, the server 160 may use the virtualized infrastructure manager 199 to facilitate backups for a plurality of virtual machines (e.g., eight different virtual machines) running on the server 160. Each virtual machine running on the server 160 may run its own guest operating system and its own set of applications. Each virtual machine running on the server 160 may store its own set of files using one or more virtual disks associated with the virtual machine (e.g., each virtual machine may include two virtual disks that are used for storing data associated with the virtual machine).

In one embodiment, a data management application running on a storage appliance, such as storage appliance 140 in FIG. 1A or storage appliance 170 in FIG. 1A, may request a snapshot of a virtual machine running on server 160. The snapshot of the virtual machine may be stored as one or more files, with each file associated with a virtual disk of the virtual machine. A snapshot of a virtual machine may correspond with a state of the virtual machine at a particular point in time. The particular point in time may be associated with a time stamp. In one example, a first snapshot of a virtual machine may correspond with a first state of the virtual machine (including the state of applications and files stored on the virtual machine) at a first point in time (e.g., 6:30 p.m. on Jun. 29, 2017) and a second snapshot of the virtual machine may correspond with a second state of the virtual machine at a second point in time subsequent to the first point in time (e.g., 6:30 p.m. on Jun. 30, 2017).

In response to a request for a snapshot of a virtual machine at a particular point in time, the virtualized infrastructure manager 199 may set the virtual machine into a frozen state or store a copy of the virtual machine at the particular point in time. The virtualized infrastructure manager 199 may then transfer data associated with the virtual machine (e.g., an image of the virtual machine or a portion of the image of the virtual machine) to the storage appliance. The data associated with the virtual machine may include a set of files including a virtual disk file storing contents of a virtual disk of the virtual machine at the particular point in time and a virtual machine configuration file storing configuration settings for the virtual machine at the particular point in time. The contents of the virtual disk file may include the operating system used by the virtual machine, local applications stored on the virtual disk, and user files (e.g., images and word processing documents). In some cases, the virtualized infrastructure manager 199 may transfer a full image of the virtual machine to the storage appliance or a plurality of data blocks corresponding with the full image (e.g., to enable a full image-level backup of the virtual machine to be stored on the storage appliance). In other cases, the virtualized infrastructure manager 199 may transfer a portion of an image of the virtual machine associated with data that has changed since an earlier point in time prior to the particular point in time or since a last snapshot of the virtual machine was taken. In one example, the virtualized infrastructure manager 199 may transfer only data associated with changed blocks stored on a virtual disk of the virtual machine that have changed since the last snapshot of the virtual machine was taken. In one embodiment, the data management application may specify a first point in time and a second point in time and the virtualized infrastructure manager 199 may output one or more changed data blocks associated with the virtual machine that have been modified between the first point in time and the second point in time.

FIG. 1C depicts one embodiment of a storage appliance, such as storage appliance 170 in FIG. 1A. The storage appliance may include a plurality of physical machines that may be grouped together and presented as a single computing system. Each physical machine of the plurality of physical machines may comprise a node in a cluster (e.g., a failover cluster). As depicted, the storage appliance 170 includes hardware-level components and software-level components. The hardware-level components include one or more physical machines, such as physical machine 120 and physical machine 130. The physical machine 120 includes a network interface 121, processor 122, memory 123, and disk 124 all in communication with each other. Processor 122 allows physical machine 120 to execute computer readable instructions stored in memory 123 to perform processes described herein. Disk 124 may include a hard disk drive and/or a solid-state drive. The physical machine 130 includes a network interface 131, processor 132, memory 133, and disk 134 all in communication with each other. Processor 132 allows physical machine 130 to execute computer readable instructions stored in memory 133 to perform processes described herein. Disk 134 may include a hard disk drive and/or a solid-state drive. In some cases, disk 134 may include a flash-based SSD or a hybrid HDD/SSD drive. In one embodiment, the storage appliance 170 may include a plurality of physical machines arranged in a cluster (e.g., eight machines in a cluster). Each of the plurality of physical machines may include a plurality of multi-core CPUs, 128 GB of RAM, a 500 GB SSD, four 4 TB HDDs, and a network interface controller.

As depicted in FIG. 1C, the software-level components of the storage appliance 170 may include data management system 102, a virtualization interface 104, a distributed job scheduler 108, a distributed metadata store 110, a distributed file system 112, and one or more virtual machine search indexes, such as virtual machine search index 106. In one embodiment, the software-level components of the storage appliance 170 may be run using a dedicated hardware-based appliance. In another embodiment, the software-level components of the storage appliance 170 may be run from the cloud (e.g., the software-level components may be installed on a cloud service provider).

In some cases, the data storage across a plurality of nodes in a cluster (e.g., the data storage available from the one or more physical machines) may be aggregated and made available over a single file system namespace (e.g., /snapshots/). A directory for each virtual machine protected using the storage appliance 170 may be created (e.g., the directory for Virtual Machine A may be /snapshots/VM_A). Snapshots and other data associated with a virtual machine may reside within the directory for the virtual machine. In one example, snapshots of a virtual machine may be stored in subdirectories of the directory (e.g., a first snapshot of Virtual Machine A may reside in /snapshots/VM_A/s1/and a second snapshot of Virtual Machine A may reside in /snapshots/VM_A/s2/).

The distributed file system 112 may present itself as a single file system, in which as new physical machines or nodes are added to the storage appliance 170, the cluster may automatically discover the additional nodes and automatically increase the available capacity of the file system for storing files and other data. Each file stored in the distributed file system 112 may be partitioned into one or more chunks. Each of the one or more chunks may be stored within the distributed file system 112 as a separate file. The files stored within the distributed file system 112 may be replicated or mirrored over a plurality of physical machines, thereby creating a load-balanced and fault tolerant distributed file system. In one example, storage appliance 170 may include ten physical machines arranged as a failover cluster and a first file corresponding with a full-image snapshot of a virtual machine (e.g., /snapshots/VM_A/s1/s1.full) may be replicated and stored on three of the ten machines. In some cases, the data chunks associated with a file stored in the distributed file system 112 may include replicated data (e.g., due to n-way mirroring) or parity data (e.g., due to erasure coding). When a disk storing one of the data chunks fails, then the distributed file system may regenerate the lost data and store the lost data using a new disk.

In one embodiment, the distributed file system 112 may be used to store a set of versioned files corresponding with a virtual machine. The set of versioned files may include a first file comprising a full image of the virtual machine at a first point in time and a second file comprising an incremental file relative to the full image. The set of versioned files may correspond with a snapshot chain for the virtual machine. The distributed file system 112 may determine a first set of data chunks that includes redundant information for the first file (e.g., via application of erasure code techniques) and store the first set of data chunks across a plurality of nodes within a cluster. The placement of the first set of data chunks within the cluster may be determined based on the locations of other data related to the first set of data chunks (e.g., the locations of other chunks corresponding with the second file or other files within the snapshot chain for the virtual machine). In some embodiments, the distributed file system 112 may also co-locate data chunks or replicas of virtual machines discovered to be similar to each other in order to allow for cross virtual machine deduplication. In this case, the placement of the first set of data chunks may be determined based on the locations of other data corresponding with a different virtual machine that has been determined to be sufficiently similar to the virtual machine.

The distributed metadata store 110 may comprise a distributed database management system that provides high availability without a single point of failure. The distributed metadata store 110 may act as a quick-access database for various components in the software stack of the storage appliance 170 and may store metadata corresponding with stored snapshots using a solid-state storage device, such as a solid-state drive (SSD) or a Flash-based storage device. In one embodiment, the distributed metadata store 110 may comprise a database, such as a distributed document oriented database. The distributed metadata store 110 may be used as a distributed key value storage system. In one example, the distributed metadata store 110 may comprise a distributed NoSQL key value store database. In some cases, the distributed metadata store 110 may include a partitioned row store, in which rows are organized into tables or other collections of related data held within a structured format within the key value store database. A table (or a set of tables) may be used to store metadata information associated with one or more files stored within the distributed file system 112. The metadata information may include the name of a file, a size of the file, file permissions associated with the file, when the file was last modified, and file mapping information associated with an identification of the location of the file stored within a cluster of physical machines. In one embodiment, a new file corresponding with a snapshot of a virtual machine may be stored within the distributed file system 112 and metadata associated with the new file may be stored within the distributed metadata store 110. The distributed metadata store 110 may also be used to store a backup schedule for the virtual machine and a list of snapshots for the virtual machine that are stored using the storage appliance 170.

In some cases, the distributed metadata store 110 may be used to manage one or more versions of a virtual machine. The concepts described herein may also be applicable to managing versions of a real machine or versions of electronic files. Each version of the virtual machine may correspond with a full image snapshot of the virtual machine stored within the distributed file system 112 or an incremental snapshot of the virtual machine (e.g., a forward incremental or reverse incremental) stored within the distributed file system 112. In one embodiment, the one or more versions of the virtual machine may correspond with a plurality of files. The plurality of files may include a single full image snapshot of the virtual machine and one or more incrementals derived from the single full image snapshot. The single full image snapshot of the virtual machine may be stored using a first storage device of a first type (e.g., a HDD) and the one or more incrementals derived from the single full image snapshot may be stored using a second storage device of a second type (e.g., an SSD). In this case, only a single full image needs to be stored and each version of the virtual machine may be generated from the single full image or the single full image combined with a subset of the one or more incrementals. Furthermore, each version of the virtual machine may be generated by performing a sequential read from the first storage device (e.g., reading a single file from a HDD) to acquire the full image and, in parallel, performing one or more reads from the second storage device (e.g., performing fast random reads from an SSD) to acquire the one or more incrementals. In some cases, a first version of a virtual machine corresponding with a first snapshot of the virtual machine at a first point in time may be generated by concurrently reading a full image for the virtual machine corresponding with a state of the virtual machine prior to the first point in time from the first storage device while reading one or more incrementals from the second storage device different from the first storage device (e.g., reading the full image from a HDD at the same time as reading 64 incrementals from an SSD).

The distributed job scheduler 108 may comprise a distributed fault tolerant job scheduler, in which jobs affected by node failures are recovered and rescheduled to be run on available nodes. In one embodiment, the distributed job scheduler 108 may be fully decentralized and implemented without the existence of a master node. The distributed job scheduler 108 may run job scheduling processes on each node in a cluster or on a plurality of nodes in the cluster and each node may independently determine which tasks to execute. The distributed job scheduler 108 may be used for scheduling backup jobs that acquire and store virtual machine snapshots for one or more virtual machines over time. The distributed job scheduler 108 may follow a backup schedule to backup an entire image of a virtual machine at a particular point in time or one or more virtual disks associated with the virtual machine at the particular point in time.

The job scheduling processes running on at least a plurality of nodes in a cluster (e.g., on each available node in the cluster) may manage the scheduling and execution of a plurality of jobs. The job scheduling processes may include run processes for running jobs, cleanup processes for cleaning up failed tasks, and rollback processes for rolling-back or undoing any actions or tasks performed by failed jobs. In one embodiment, the job scheduling processes may detect that a particular task for a particular job has failed and in response may perform a cleanup process to clean up or remove the effects of the particular task and then perform a rollback process that processes one or more completed tasks for the particular job in reverse order to undo the effects of the one or more completed tasks. Once the particular job with the failed task has been undone, the job scheduling processes may restart the particular job on an available node in the cluster.

The virtualization interface 104 may provide an interface for communicating with a virtualized infrastructure manager managing a virtualized infrastructure, such as the virtualized infrastructure manager 199 in FIG. 1B, and for requesting data associated with virtual machine snapshots from the virtualized infrastructure. The virtualization interface 104 may communicate with the virtualized infrastructure manager using an API for accessing the virtualized infrastructure manager (e.g., to communicate a request for a snapshot of a virtual machine).

The virtual machine search index 106 may include a list of files that have been stored using a virtual machine and a version history for each of the files in the list. Each version of a file may be mapped to the earliest point in time snapshot of the virtual machine that includes the version of the file or to a snapshot of the virtual machine that includes the version of the file (e.g., the latest point in time snapshot of the virtual machine that includes the version of the file). In one example, the virtual machine search index 106 may be used to identify a version of the virtual machine that includes a particular version of a file (e.g., a particular version of a database, a spreadsheet, or a word processing document). In some cases, each of the virtual machines that are backed up or protected using storage appliance 170 may have a corresponding virtual machine search index.

The data management system 102 may comprise an application running on the storage appliance that manages the capturing, storing, deduplication, compression (e.g., using a lossless data compression algorithm such as LZ4 or LZ77), and encryption (e.g., using a symmetric key algorithm such as Triple DES or AES-256) of data for the storage appliance 170. In one example, the data management system 102 may comprise a highest level layer in an integrated software stack running on the storage appliance. The integrated software stack may include the data management system 102, the virtualization interface 104, the distributed job scheduler 108, the distributed metadata store 110, and the distributed file system 112. In some cases, the integrated software stack may run on other computing devices, such as a server or computing device 154 in FIG. 1A. The data management system 102 may use the virtualization interface 104, the distributed job scheduler 108, the distributed metadata store 110, and the distributed file system 112 to manage and store one or more snapshots of a virtual machine. Each snapshot of the virtual machine may correspond with a point in time version of the virtual machine. The data management system 102 may generate and manage a list of versions for the virtual machine. Each version of the virtual machine may map to or reference one or more chunks and/or one or more files stored within the distributed file system 112. Combined together, the one or more chunks and/or the one or more files stored within the distributed file system 112 may comprise a full image of the version of the virtual machine.

In some embodiments, a plurality of versions of a virtual machine may be stored as a base file associated with a complete image of the virtual machine at a particular point in time and one or more incremental files associated with forward and/or reverse incremental changes derived from the base file. The data management system 102 may patch together the base file and the one or more incremental files in order to generate a particular version of the plurality of versions by adding and/or subtracting data associated with the one or more incremental files from the base file or intermediary files derived from the base file. In some embodiments, each version of the plurality of versions of a virtual machine may correspond with a merged file. A merged file may include pointers or references to one or more files and/or one or more chunks associated with a particular version of a virtual machine. In one example, a merged file may include a first pointer or symbolic link to a base file and a second pointer or symbolic link to an incremental file associated with the particular version of the virtual machine. In some embodiments, the one or more incremental files may correspond with forward incrementals (e.g., positive deltas), reverse incrementals (e.g., negative deltas), or a combination of both forward incrementals and reverse incrementals.

FIG. 1D depicts one embodiment of a portion of an integrated data management and storage system that includes a plurality of nodes in communication with each other and one or more storage devices via one or more networks 180. The plurality of nodes may be networked together and present themselves as a unified storage system. The plurality of nodes includes node 141 and node 147. The one or more storage devices include storage device 157 and storage device 158. Storage device 157 may correspond with a cloud-based storage (e.g., private or public cloud storage). Storage device 158 may comprise a hard disk drive (HDD), a magnetic tape drive, a solid-state drive (SSD), a storage area network (SAN) storage device, or a networked-attached storage (NAS) device. The integrated data management and storage system may comprise a distributed cluster of storage appliances in which each of the storage appliances includes one or more nodes. In one embodiment, node 141 and node 147 may comprise two nodes housed within a first storage appliance, such as storage appliance 170 in FIG. 1C. In another embodiment, node 141 may comprise a first node housed within a first storage appliance and node 147 may comprise a second node housed within a second storage appliance different from the first storage appliance. The first storage appliance and the second storage appliance may be located within a data center, such as data center 150 in FIG. 1A, or located within different data centers.

As depicted, node 141 includes a network interface 142, a node controller 143, and a first plurality of storage devices including HDDs 144-145 and SSD 146. The first plurality of storage devices may comprise two or more different types of storage devices. The node controller 143 may comprise one or more processors configured to store, deduplicate, compress, and/or encrypt data stored within the first plurality of storage devices. Node 147 includes a network interface 148, a node controller 149, and a second plurality of storage devices including HDDs 151-152 and SSD 153. The second plurality of storage devices may comprise two or more different types of storage devices. The node controller 149 may comprise one or more processors configured to store, deduplicate, compress, and/or encrypt data stored within the second plurality of storage devices. In some cases, node 141 may correspond with physical machine 120 in FIG. 1C and node 147 may correspond with physical machine 130 in FIG. 1C.

FIGS. 2A-2K depict various embodiments of sets of files and data structures (e.g., implemented using merged files) associated with managing and storing snapshots of virtual machines. Although various embodiments may be described in reference to the management of virtual machine snapshots, the concepts may be applied to the management of other data snapshots as well, such as snapshots of databases, filesets (e.g., Network Attached Storage filesets), and sets of electronic files.

FIG. 2A depicts one embodiment of a set of virtual machine snapshots stored as a first set of files. The first set of files may be stored using a distributed file system, such as distributed file system 112 in FIG. 1C. As depicted, the first set of files includes a set of reverse incrementals (R1-R4), a full image (Base), and a set of forward incrementals (F1-F2). The set of virtual machine snapshots includes different versions of a virtual machine (versions V1-V7 of Virtual Machine A) captured at different points in time (times T1-T7). In some cases, the file size of the reverse incremental R3 and the file size of the forward incremental F2 may both be less than the file size of the base image corresponding with version V5 of Virtual Machine A. The base image corresponding with version V5 of Virtual Machine A may comprise a full image of Virtual Machine A at point in time T5. The base image may include a virtual disk file for Virtual Machine A at point in time T5. The reverse incremental R3 corresponds with version V2 of Virtual Machine A and the forward incremental F2 corresponds with version V7 of Virtual Machine A. The forward incremental F1 may be associated with the data changes that occurred to Virtual Machine A between time T5 and time T6 and may comprise one or more changed data blocks.

In some embodiments, each snapshot of the set of virtual machine snapshots may be stored within a storage appliance, such as storage appliance 170 in FIG. 1A. In other embodiments, a first set of the set of virtual machine snapshots may be stored within a first storage appliance and a second set of the set of virtual machine snapshots may be stored within a second storage appliance, such as storage appliance 140 in FIG. 1A. In this case, a data management system may extend across both the first storage appliance and the second storage appliance. In one example, the first set of the set of virtual machine snapshots may be stored within a local cluster repository (e.g., recent snapshots of the file may be located within a first data center) and the second set of the set of virtual machine snapshots may be stored within a remote cluster repository (e.g., older snapshots or archived snapshots of the file may be located within a second data center) or a cloud repository.

FIG. 2B depicts one embodiment of a merged file for generating version V7 of Virtual Machine A using the first set of files depicted in FIG. 2A. The merged file includes a first pointer (pBase) that references the base image Base (e.g., via the path /snapshots/VM_A/s5/s5.full), a second pointer (pF1) that references the forward incremental F1 (e.g., via the path /snapshots/VM_A/s6/s6.delta), and a third pointer (pF2) that references the forward incremental F2 (e.g., via the path /snapshots/VM_A/s7/s7.delta). In one embodiment, to generate the full image of version V7 of Virtual Machine A, the base image may be acquired, the data changes associated with forward incremental F1 may be applied to (or patched to) the base image to generate an intermediate image, and then the data changes associated with forward incremental F2 may be applied to the intermediate image to generate the full image of version V7 of Virtual Machine A.

FIG. 2C depicts one embodiment of a merged file for generating version V2 of Virtual Machine A using the first set of files depicted in FIG. 2A. The merged file includes a first pointer (pBase) that references the base image Base (e.g., via the path /snapshots/VM_A/s5/s5.full), a second pointer (pR1) that references the reverse incremental R1 (e.g., via the path /snapshots/VM_A/s4/s4.delta), a third pointer (pR2) that references the reverse incremental R2 (e.g., via the path /snapshots/VM_A/s3/s3.delta), and a fourth pointer (pR3) that references the reverse incremental R3 (e.g., via the path /snapshots/VM_A/s2/s2.delta). In one embodiment, to generate the full image of version V2 of Virtual Machine A, the base image may be acquired, the data changes associated with reverse incremental R1 may be applied to the base image to generate a first intermediate image, the data changes associated with reverse incremental R2 may be applied to the first intermediate image to generate a second intermediate image, and then the data changes associated with reverse incremental R3 may be applied to the second intermediate image to generate the full image of version V2 of Virtual Machine A.

FIG. 2D depicts one embodiment of a set of virtual machine snapshots stored as a second set of files after a rebasing process has been performed using the first set of files in FIG. 2A. The second set of files may be stored using a distributed file system, such as distributed file system 112 in FIG. 1C. The rebasing process may generate new files R12, R11, and Base2 associated with versions V5-V7 of Virtual Machine A in order to move a full image closer to a more recent version of Virtual Machine A and to improve the reconstruction time for the more recent versions of Virtual Machine A. The data associated with the full image Base in FIG. 2A may be equivalent to the new file R12 patched over R11 and the full image Base2. Similarly, the data associated with the full image Base2 may be equivalent to the forward incremental F2 in FIG. 2A patched over F1 and the full image Base in FIG. 2A.

The process of moving the full image snapshot for the set of virtual machine snapshots to correspond with the most recent snapshot version may be performed in order to shorten or reduce the chain lengths for the newest or most recent snapshots, which may comprise the snapshots of Virtual Machine A that are the most likely to be accessed. In some cases, a rebasing operation (e.g., that moves the full image snapshot for a set of virtual machine snapshots to correspond with the most recent snapshot version) may be triggered when a number of forward incremental files is greater than a threshold number of forward incremental files for a snapshot chain (e.g., more than 200 forward incremental files). In other cases, a rebasing operation may be triggered when the total disk size for the forward incremental files exceeds a threshold disk size (e.g., is greater than 200 GB) or is greater than a threshold percentage (e.g., is greater than 20%) of the base image for the snapshot chain.

In some cases, the rebasing process may be part of a periodic rebasing process that is applied at a rebasing frequency (e.g., every 24 hours) to each virtual machine of a plurality of protected virtual machines to reduce the number of forward incremental files that need to be patched to a base image in order to restore the most recent version of a virtual machine. Periodically reducing the number of forward incremental files may reduce the time to restore the most recent version of the virtual machine as the number of forward incremental files that need to be applied to a base image to generate the most recent version may be limited. In one example, if a rebasing process is applied to snapshots of a virtual machine every 24 hours and snapshots of the virtual machine are acquired every four hours, then the number of forward incremental files may be limited to at most five forward incremental files.

As depicted, the second set of files includes a set of reverse incrementals (R11-R12 and R1-R4) and a full image (Base2). The set of virtual machine snapshots includes the different versions of the virtual machine (versions V1-V7 of Virtual Machine A) captured at the different points in time (times T1-T7) depicted in FIG. 2A. In some cases, the file size of the reverse incremental R2 may be substantially less than the file size of the base image Base2. The reverse incremental R2 corresponds with version V2 of Virtual Machine A and the base image Base2 corresponds with version V7 of Virtual Machine A. In this case, the most recent version of Virtual Machine A (i.e., the most recent restore point for Virtual Machine A) comprises a full image. To generate earlier versions of Virtual Machine A, reverse incrementals may be applied to (or patched to) the full image Base2. Subsequent versions of Virtual Machine A may be stored as forward incrementals that depend from the full image Base2.

In one embodiment, a rebasing process may be applied to a first set of files associated with a virtual machine in order to generate a second set of files to replace the first set of files. The first set of files may include a first base image from which a first version of the virtual machine may be derived and a first forward incremental file from which a second version of the virtual machine may be derived. The second set of files may include a second reverse incremental file from which the first version of the virtual machine may be derived and a second base image from which the second version of the virtual machine may be derived. During the rebasing process, data integrity checking may be performed to detect and correct data errors in the files stored in a file system, such as distributed file system 112 in FIG. 1C, that are read to generate the second set of files.

FIG. 2E depicts one embodiment of a merged file for generating version V7 of Virtual Machine A using the second set of files depicted in FIG. 2D. The merged file includes a first pointer (pBase2) that references the base image Base2 (e.g., via the path /snapshots/VM_A/s7/s7.full). In this case, the full image of version V7 of Virtual Machine A may be directly acquired without patching forward incrementals or reverse incrementals to the base image Base2 corresponding with version V7 of Virtual Machine A.

FIG. 2F depicts one embodiment of a merged file for generating version V2 of Virtual Machine A using the second set of files depicted in FIG. 2D. The merged file includes a first pointer (pBase2) that references the base image Base2 (e.g., via the path /snapshots/VM_A/s7/s7.full), a second pointer (pR11) that references the reverse incremental R11 (e.g., via the path /snapshots/VM_A/s6/s6.delta), a third pointer (pR12) that references the reverse incremental R12 (e.g., via the path /snapshots/VM_A/s5/s5.delta), a fourth pointer (pR1) that references the reverse incremental R1 (e.g., via the path /snapshots/VM_A/s4/s4.delta), a fifth pointer (pR2) that references the reverse incremental R2 (e.g., via the path /snapshots/VM_A/s3/s3.delta), and a sixth pointer (pR3) that references the reverse incremental R3 (e.g., via the path /snapshots/VM_A/s2/s2.delta). In one embodiment, to generate the full image of version V2 of Virtual Machine A, the base image may be acquired, the data changes associated with reverse incremental R11 may be applied to the base image to generate a first intermediate image, the data changes associated with reverse incremental R12 may be applied to the first intermediate image to generate a second intermediate image, the data changes associated with reverse incremental R1 may be applied to the second intermediate image to generate a third intermediate image, the data changes associated with reverse incremental R2 may be applied to the third intermediate image to generate a fourth intermediate image, and then the data changes associated with reverse incremental R3 may be applied to the fourth intermediate image to generate the full image of version V2 of Virtual Machine A.

FIG. 2G depicts one embodiment of a set of files associated with multiple virtual machine snapshots. The set of files may be stored using a distributed file system, such as distributed file system 112 in FIG. 1C. As depicted, the set of files includes a second full image (BaseB), a set of forward incrementals (F1-F2 and F5-F6) that derive from the second full image (BaseB), and a set of reverse incrementals (R1-R3) that derive from the second full image (BaseB). The set of files also includes a first full image (BaseA) and a reverse incremental (R4) that derives from the first full image (BaseA). In this case, the depicted snapshots for Virtual Machine A include two different full image snapshots (BaseA and BaseB). Each of the full image snapshots may comprise an anchor snapshot for a snapshot chain. The first full image (BaseA) and the reverse incremental (R4) may comprise a first snapshot chain with the first full image acting as the anchor snapshot. A second snapshot chain may comprise the second full image (BaseB) acting as the anchor snapshot for the second snapshot chain, the set of forward incrementals (F1-F2), and the set of reverse incrementals (R1-R3). The first snapshot chain and the second snapshot chain may be independent of each other and independently managed. For example, the base image associated with the second snapshot chain for Virtual Machine A may be repositioned (e.g., via rebasing) without impacting the first snapshot chain for Virtual Machine A.

A third snapshot chain for Virtual Machine C may comprise the second full image (BaseB) and forward incrementals (F1 and F5-F6). The first snapshot chain for Virtual Machine A and the third snapshot chain for Virtual Machine C may be independent of each other and independently managed. However, as Virtual Machine C is a dependent virtual machine that depends from the second snapshot chain for Virtual Machine A, changes to the second snapshot chain may impact the third snapshot chain. For example, repositioning of the base image for the second snapshot chain due to rebasing may require the merged files for the third snapshot chain to be updated.

In some embodiments, each of the snapshot chains for Virtual Machine A may have a maximum incremental chain length (e.g., no more than 100 total incremental files), a maximum reverse incremental chain length (e.g., no more than 50 reverse incremental files), and a maximum forward incremental chain length (e.g., no more than 70 forward incremental files. In the event that a new snapshot will cause one of the snapshot chains to violate the maximum incremental chain length, the maximum reverse incremental chain length, or the maximum forward incremental chain length, then a new snapshot chain may be created for Virtual Machine A and a new full-image base file may be stored for the new snapshot chain.

FIG. 2H depicts one embodiment of a merged file for generating version VS of Virtual Machine A using the set of files depicted in FIG. 2G. The merged file includes a first pointer (pBaseA) that references the first base image BaseA and a second pointer (pR4) that references the reverse incremental R4. In one embodiment, to generate the full image of version VS of Virtual Machine A, the first base image associated with Version VT of Virtual Machine A may be acquired and the data changes associated with reverse incremental R4 may be applied to the first base image to generate the full image of version VS of Virtual Machine A.

FIG. 2I depicts one embodiment of a merged file for generating version VU of Virtual Machine A using the set of files depicted in FIG. 2G. The merged file includes a first pointer (pBaseB) that references the second base image BaseB, a second pointer (pR1) that references the reverse incremental R1, a third pointer (pR2) that references the reverse incremental R2, and a fourth pointer (pR3) that references the reverse incremental R3. In one embodiment, to generate the full image of version VU of Virtual Machine A, the second base image associated with Version VY of Virtual Machine A may be acquired, the data changes associated with reverse incremental R1 may be applied to the second base image to generate a first intermediate image, the data changes associated with reverse incremental R2 may be applied to the first intermediate image to generate a second intermediate image, and the data changes associated with reverse incremental R3 may be applied to the second intermediate image to generate the full image of version VU of Virtual Machine A.

FIG. 2J depicts one embodiment of a set of files associated with multiple virtual machine snapshots after a rebasing process has been performed to a snapshot chain using the set of files in FIG. 2G. The set of files may be stored using a distributed file system, such as distributed file system 112 in FIG. 1C. The rebasing process may generate new files R12, R11, and BaseB2. As depicted, the set of files includes a set of reverse incrementals (R11-R12 and R1-R2), a full image (BaseB2), and a set of forward incrementals (F5-F7). In this case, a second version of Virtual Machine C may be generated using forward incrementals F5-F6 that are derived from Version VZ of Virtual Machine A. Forward incremental file F7 may include changes to Version VW of Virtual Machine A that occurred subsequent to the generation of the full image file BaseB2. In some cases, the forward incremental file F7 may comprise a writeable file or have file permissions allowing modification of the file, while all other files associated with earlier versions of Virtual Machine A comprise read only files.

FIG. 2K depicts one embodiment of a merged file for generating version VU of Virtual Machine A using the set of files depicted in FIG. 2J. The merged file includes a first pointer (pBaseA) that references the first base image BaseA and a second pointer (pF9) that references the forward incremental F9. In one embodiment, to generate the full image of version VU of Virtual Machine A, the first base image associated with Version VT of Virtual Machine A may be acquired and the data changes associated with forward incremental F9 may be applied to the first base image to generate the full image of version VU of Virtual Machine A.

In some embodiments, upon detection that a second snapshot chain has reached a maximum incremental chain length (e.g., no more than 500 total incremental files), a maximum reverse incremental chain length (e.g., no more than 400 reverse incremental files), or a maximum forward incremental chain length (e.g., no more than 150 forward incremental files), an existing snapshot chain (e.g., the first snapshot chain depicted in FIG. 2J) may have its chain length extended or snapshots previously assigned to the second snapshot chain may be moved to the existing snapshot chain. For example, the first snapshot chain depicted in FIG. 2G comprises two total snapshots, while the first snapshot chain depicted in FIG. 2J comprises three total snapshots as the snapshot corresponding with version VU of Virtual Machine A has moved from the second snapshot chain to the first snapshot chain.

In some embodiments, the number of snapshots in a snapshot chain may decrease over time as older versions of a virtual machine are consolidated, archived, deleted, or moved to a different storage domain (e.g., to cloud storage) depending on the data backup and archiving schedule for the virtual machine. In some cases, the maximum incremental chain length or the maximum number of snapshots for a snapshot chain may be increased over time as the versions stored by the snapshot chain age. In one example, if the versions of a virtual machine stored using a snapshot chain are all less than one month old, then the maximum incremental chain length may be set to a maximum of 200 incrementals; however, if the versions of the virtual machine stored using the snapshot chain are all greater than one month old, then the maximum incremental chain length may be set to a maximum of 1000 incrementals.

In some embodiments, the maximum incremental chain length for a snapshot chain may be increased over time as the number of allowed snapshots in a snapshot chain may be increased as the backed-up versions of a virtual machine get older. For example, the maximum incremental chain length for a snapshot chain storing versions of a virtual machine that are less than one year old may comprise a maximum incremental chain length of 200 incrementals, while the maximum incremental chain length for a snapshot chain storing versions of a virtual machine that are more than one year old may comprise a maximum incremental chain length of 500 incrementals.

FIG. 3A is a flowchart describing one embodiment of a process for managing and storing virtual machine snapshots using a data storage system. In one embodiment, the process of FIG. 3A may be performed by a storage appliance, such as storage appliance 170 in FIG. 1A.

In step 302, a schedule for backing up a first virtual machine is determined. In one example, the schedule for backing up the first virtual machine may comprise periodically backing up the first virtual machine every four hours. The schedule for backing up the first virtual machine may be derived from a new backup, replication, and archival policy or backup class assigned to the first virtual machine. In step 304, a job scheduler is configured to implement the schedule for backing up the first virtual machine. In one example, a distributed job scheduler, such as distributed job scheduler 108 in FIG. 1C, may be configured to schedule and run processes for capturing and storing images of the first virtual machine over time according the schedule. In step 306, a snapshot process for acquiring a snapshot of the first virtual machine is initiated. The snapshot process may send an instruction to a virtualized infrastructure manager, such as virtualization manager 169 in FIG. 1A, that requests data associated with the snapshot of the first virtual machine. In step 308, a type of snapshot to be stored is determined. The type of snapshot may comprise a full image snapshot or an incremental snapshot. In some cases, a full image snapshot may be captured and stored in order to serve as an anchor snapshot for a new snapshot chain. Versions of the first virtual machine may be stored using one or more independent snapshot chains, wherein each snapshot chain comprises a full image snapshot and one or more incremental snapshots. One embodiment of a process for determining the type of snapshot to be stored (e.g., storing either a full image snapshot or an incremental snapshot) is described later in reference to FIG. 3B.

In step 310, it is determined whether a full image of the first virtual machine needs to be stored in order to store the snapshot of the first virtual machine. The determination of whether a full image is required may depend on whether a previous full image associated with a prior version of the first virtual machine has been acquired. The determination of whether a full image is required may depend on the determination of the type of snapshot to be stored in step 308. If a full image needs to be stored, then step 311 is performed. Otherwise, if a full image does not need to be stored, then step 312 is performed. In step 311, the full image of the first virtual machine is acquired. The full image of the first virtual machine may correspond with a file or one or more data chunks. In step 312, changes relative to a prior version of the first virtual machine or relative to another virtual machine (e.g., in the case that the first virtual machine comprises a dependent virtual machine whose snapshots derive from a full image snapshot of a second virtual machine different from the first virtual machine) are acquired. The changes relative to the prior version of the first virtual machine or relative to a version of a different virtual machine may correspond with a file or one or more data chunks. In step 313, the full image of the first virtual machine is stored using a distributed file system, such as distributed file system 112 in FIG. 1C. In step 314, the changes relative to the prior version of the first virtual machine or relative to another virtual machine are stored using a distributed file system, such as distributed file system 112 in FIG. 1C. In one embodiment, the full image of the first virtual machine may be stored using a first storage device of a first type (e.g., a HDD) and the changes relative to the prior version of the first virtual machine may be stored using a second storage device of a second type (e.g., an SSD).

In some embodiments, snapshots of the first virtual machine may be ingested at a snapshot capture frequency (e.g., every 30 minutes) by a data storage system. When a snapshot of the first virtual machine is ingested, the snapshot may be compared with other snapshots stored within the data storage system in order to identify a candidate snapshot from which the snapshot may depend. In one example, a scalable approximate matching algorithm may be used to identify the candidate snapshot whose data most closely matches the data associated with the snapshot or to identify the candidate snapshot whose data has the fewest number of data differences with the snapshot. In another example, an approximate matching algorithm may be used to identify the candidate snapshot whose data within a first portion of the candidate snapshot most closely matches data associated with a first portion of the snapshot. In some cases, a majority of the data associated with the snapshot and the candidate snapshot may be identical (e.g., both the snapshot and the candidate snapshot may be associated with virtual machines that use the same operating system and have the same applications installed). Once the candidate snapshot has been identified, then data differences (or the delta) between the snapshot and the candidate snapshot may be determined and the snapshot may be stored based on the data differences. In one example, the snapshot may be stored using a forward incremental file that includes the data differences between the snapshot and the candidate snapshot. The forward incremental file may be compressed prior to being stored within a file system, such as distributed file system 112 in FIG. 1C.

In step 316, a merged file associated with the snapshot is generated. The merged file may reference one or more files or one or more data chunks that have been acquired in either step 311 or step 312. In one example, the merged file may comprise a file or a portion of a file that includes pointers to the one or more files or the one or more data chunks. In step 318, the merged file is stored in a metadata store, such as distributed metadata store 110 in FIG. 1C. In step 320, a virtual machine search index for the first virtual machine is updated. The virtual machine search index for the first virtual machine may include a list of files that have been stored in the first virtual machine and a version history for each of the files in the list. In one example, the virtual machine search index for the first virtual machine may be updated to include new files that have been added to the first virtual machine since a prior snapshot of the first virtual machine was taken and/or to include updated versions of files that were previously stored in the first virtual machine.

FIG. 3B is a flowchart describing one embodiment of a process for determining the type of snapshot to be stored using a data storage system. The process described in FIG. 3B is one example of a process for implementing step 308 in FIG. 3A. In one embodiment, the process of FIG. 3B may be performed by a storage appliance, such as storage appliance 170 in FIG. 1A.

In step 332, a snapshot chain for a first virtual machine is identified. The snapshot chain may comprise a full image snapshot for the first virtual machine and one or more incremental snapshots that derive from the full image snapshot. Backed-up versions of the first virtual machine may correspond with one or more snapshot chains. Each of the one or more snapshot chains may include a full image snapshot or a base image from which incremental snapshots may derive.

In step 334, it is determined whether the snapshot chain includes a dependent base file. In this case, the first virtual machine may comprise a dependent virtual machine that has snapshots that derive from a full image snapshot of a different virtual machine. In one embodiment, the first virtual machine and the different virtual machine from which the first virtual machine depends may each have different virtual machine configuration files for storing configuration settings for the virtual machines. In one example, the first virtual machine may have a first number of virtual processors (e.g., two processors) and the different virtual machine may have a second number of virtual processors different from the first number of virtual processors (e.g., four processors). In another example, the first virtual machine may have a first virtual memory size (e.g., 1 GB) and the different virtual machine may have a second virtual memory size different from the first virtual memory size (e.g., 2 GB). In another example, the first virtual machine may run a first guest operating system and the different virtual machine may run a second guest operating system different from the first guest operating system.

In step 336, a maximum incremental chain length for the snapshot chain is determined based on whether the snapshot chain includes a dependent base file. In one example, if the first virtual machine comprises a dependent virtual machine, then the maximum incremental chain length may be set to a maximum length of 200 snapshots; however if the first virtual machine is independent and is not a dependent virtual machine, then the maximum incremental chain length may be set to a maximum length of 500 snapshots.

In one embodiment, the maximum incremental chain length for the snapshot chain may be determined based on an age of the backed-up versions within the snapshot chain. In one example, the maximum incremental chain length for a snapshot chain storing versions of the first virtual machine that are less than one year old may comprise a maximum incremental chain length of 100 incrementals, while the maximum incremental chain length for a snapshot chain storing versions of the first virtual machine that are more than one year old may comprise a maximum incremental chain length of 200 incrementals.

In step 338, it is determined whether a new snapshot chain should be created based on the maximum incremental chain length. In step 340, a type of snapshot to be stored for the first virtual machine is determined based on the maximum incremental chain length. The type of snapshot may comprise either a full image snapshot or an incremental snapshot. In one embodiment, if the snapshot chain for the first virtual machine exceeds the maximum incremental chain length for the snapshot chain, then the type of snapshot to be stored for the first virtual machine may comprise a full image snapshot. In this case, an additional snapshot chain may be created for the first virtual machine.

In some embodiments, the number of snapshots in a snapshot chain may decrease over time as older versions of a virtual machine are consolidated, archived, deleted, or moved to a different storage domain (e.g., to cloud storage) depending on the data backup and archiving schedule for the virtual machine. In some cases, the maximum incremental chain length or the maximum number of snapshots for a snapshot chain may be increased over time as the versions stored by the snapshot chain age. In one example, if the versions of a virtual machine stored using a snapshot chain are all less than one month old, then the maximum incremental chain length may be set to a maximum of 200 incrementals; however, if the versions of the virtual machine stored using the snapshot chain are all greater than one month old, then the maximum incremental chain length may be set to a maximum of 1000 incrementals.

FIG. 3C is a flowchart describing one embodiment of a process for restoring a version of a virtual machine using a data storage system. In one embodiment, the process of FIG. 3C may be performed by a storage appliance, such as storage appliance 170 in FIG. 1A.

In step 382, a particular version of a virtual machine to be restored is identified. In step 384, a base image from which the particular version may be derived is determined. In step 386, a set of incremental files for generating the particular version is determined. In one embodiment, the base image and the set of incremental files may be determined from a merged file associated with the particular version of the virtual machine. In some cases, the set of incremental files may include one or more forward incremental files and/or one or more reverse incremental files. In step 388, a file associated with the particular version is generated using the base image and the set of incremental files. The file may be generated by patching the set of incremental files onto the base image. In step 390, at least a portion of the file is outputted. The at least a portion of the file may be electronically transferred to a computing device, such as computing device 154 in FIG. 1A, or to a virtualization manager, such as virtualization manager 169 in FIG. 1A.

In some embodiments, the base image and a subset of the set of incremental files may correspond with a second virtual machine different from the virtual machine. In this case, the base image may comprise the base image for the second virtual machine and the set of incremental files may include a dependent base file that comprises data differences between the base image for the second virtual machine and a previously acquired base image for the virtual machine.

FIG. 4A depicts one embodiment of a portion of an integrated data management and storage system that includes a plurality of nodes in communication with each other, a server 402, and a WORM compliant storage device 410 via one or more networks 180. The plurality of nodes may be networked together and present themselves as a unified storage system. The plurality of nodes includes node 404 and node 405. Although only two nodes are depicted in FIG. 4A, the number of nodes within the data storage cluster may comprise more than two nodes (e.g., four nodes or eight nodes). The server 402 may comprise a hardware server (e.g., acting as a production server). The WORM compliant storage 410 may comprise WORM complaint storage in the cloud or a hardware storage device that satisfies WORM compliance. The WORM compliant storage 410 may comprise a hard disk drive (HDD), a magnetic tape drive, a solid-state drive (SSD), a storage area network (SAN) storage device, or a networked-attached storage (NAS) device with immutable data storage or the ability to apply time-based data lock policies. The integrated data management and storage system may comprise a distributed cluster of storage appliances in which each of the storage appliances includes one or more nodes. In one embodiment, node 404 and node 405 may comprise two nodes housed within a first storage appliance, such as storage appliance 170 in FIG. 1C. In another embodiment, node 404 may comprise a first node housed within a first storage appliance and node 405 may comprise a second node housed within a second storage appliance different from the first storage appliance. The first storage appliance and the second storage appliance may be located within a data center, such as data center 150 in FIG. 1A, or located within different data centers.

As depicted, node 404 includes a plurality of storage devices including HDDs 411-412, SSD 413, and WORM compliant data storage 415-416. In one example, the WORM compliant data storage 415-416 may comprise one or more WORM compliant hardware data storage drives or a WORM compliant semiconductor memory. Node 405 includes a plurality of storage devices including HDDs 421-422, SSD 423, and WORM compliant data storage 425-426. In some cases, node 404 may correspond with physical machine 120 in FIG. 1C with the addition of WORM compliant hardware data storage and node 405 may correspond with physical machine 130 in FIG. 1C with the addition of WORM compliant hardware data storage.

In some embodiments, the plurality of nodes of the integrated data management and storage system including nodes 404-405 may acquire data to be backed up from server 402 (e.g., a production server). The data to be backed up may be replicated across different nodes within the plurality of nodes. In some cases, the data to be backed up may be replicated using nodes within the plurality of nodes and the external WORM compliant storage 410. The data to be backed up from server 402 may comprise one or more electronic files associated with virtual machine snapshots or real machine snapshots. In one embodiment, if a snapshot of a virtual machine is acquired from the server 402 while an earlier version of the virtual machine is locked or has been placed under WORM compliance, then the snapshot may be directly written to WORM compliant data storage, such as WORM compliant data storage 415, based on the size of the snapshot. In one example, if the size of the snapshot is greater than a threshold data size (e.g., is greater than 100 MB), then the snapshot may be directly written to the WORM compliant data storage; otherwise, if the size of the snapshot is not greater than the threshold data size, then the snapshot may be written to an SSD or a HDD that is not WORM compliant, such as SSD 413. In this case, the file access attributes for one or more electronic files associated with the snapshot may be set such that the one or more electronic files are locked and cannot be altered.

From a resource efficiency perspective, a locked file created to comply with a particular data retention policy should only be maintained as long as needed to comply with the required data retention period. As an example, the particular data retention policy may correspond with a legal hold on the file in order to lock the file or prevent data changes from being applied to the file. The data retention end date, the data retention start date, and/or the data retention period may be stored as metadata along with the locked file. Upon detection that the data retention period has expired (e.g., by comparing the data retention end date with the current date), the data access permissions for the file may be modified to allow for alterations to be made to the file.

In some embodiments, a set of data (e.g., one or more electronic files) acquired from server 402 may be stored and replicated across different nodes within the plurality of nodes of the integrated data management and storage system. In one example, upon detection that the set of data should be locked for a data retention period, a first copy of the set of data may be stored using WORM compliant data storage 415 and a second copy of the set of data may be stored using WORM compliant data storage 425. In this case, both the first copy and the second copy of the set of data may be stored using WORM compliant hardware data storage.

FIG. 4B depicts one embodiment of the portion of the integrated data management and storage system of FIG. 4A. As depicted, upon detection that the set of data should be locked for the data retention period, the first copy of the set of data may be stored using WORM compliant data storage 415 and the second copy of the set of data may be stored using HDD 421 with restricted read access permissions set for the set of data. In this case, the first copy of the set of data may be stored using a WORM compliant hardware data storage device while the second copy of the set of data may be stored using a HDD with restricted read access permissions set for the second copy of the set of data. One benefit of storing the second copy of the set of data using the HDD 421 is that read performance for the set of data may be improved compared with storing the second copy of the set of data using a WORM compliant hardware data storage device such as WORM compliant data storage 425.

FIG. 4C depicts another embodiment of the portion of the integrated data management and storage system of FIG. 4A that includes a plurality of nodes in communication with each other, a server 402, and a WORM compliant storage device 410 via one or more networks 180. The plurality of nodes includes node 405 and node 434. The node 434 includes a virtual machine 435, a virtual disk 436, and virtual WORM compliant data storage 437 in which all data that is written to the virtual WORM compliant data storage 437 is locked via restricted read access permissions. As depicted, upon detection that the set of data should be locked for the data retention period, the first copy of the set of data may be stored using WORM compliant data storage 425 and the second copy of the set of data may be stored using the virtual WORM compliant data storage 437.

FIG. 5A is a flowchart describing one embodiment of a process for operating a data storage cluster. In one embodiment, the process of FIG. 5A may be performed by a storage appliance, such as storage appliance 170 or storage appliance 140 in FIG. 1A. The process of FIG. 5A may be performed by a data storage node, such as data storage node 404 in FIG. 4A, or the integrated data management and storage system depicted in FIG. 4A that includes data storage node 404.

In step 502, a data retention time for a set of data to be WORM compliant is determined. The set of data may comprise one or more electronic files. In one example, the one or more electronic files may correspond with a virtual machine snapshot or a real machine snapshot. In another example, the one or more electronic files may correspond with all of the files stored within a particular directory. The WORM compliance may require that the set of data be immutable for the data retention time (e.g., cannot be altered for six months). In step 504, a data size for the set of data is determined. In one example, the data size may comprise an aggregate file size for a plurality of electronic files that comprises the set of data. In step 506, a storage cost for storing the set of data using a WORM compliant hardware storage device is determined based on the data size for the set of data and the data retention time for the set of data. In one example, the storage cost may correspond with the cost to store the set of data using cloud-based WORM data storage. In some embodiments, upon detection that a storage cost for storing the set of data using cloud-based WORM compliant storage is less than a threshold cost, the set of data may be transferred to the cloud-based WORM compliant storage or a replicated copy of the set of data may be transferred to the cloud-based WORM compliant storage.

In one embodiment, a data storage cluster may dynamically apply a combination of hardware-based techniques (e.g., writing data to internal WORM compliant hardware data storage) and software-based techniques (e.g., modifying file access permissions to data stored within the data storage and cluster) to satisfy WORM compliance for the set of data based on the data retention time for the set of data and the data size for the set of data.

In step 508, it is determined whether the set of data should be stored using the WORM compliant hardware storage device. The WORM compliant hardware storage device may correspond with WORM compliant hardware storage device 415 in FIG. 4A. In one embodiment, it may be determined whether the set of data should be stored using the WORM compliant hardware storage device or if the set of data should instead satisfy WORM compliance by modifying the file access permissions to prevent the stored set of data from being modified. In one example, if the data retention time is greater than a threshold data retention time (e.g., is greater than one week), then it may be determined that the set of data should be written to the WORM compliant hardware storage device; otherwise, if the data retention time is not greater than the threshold data retention time, then it may be determined that the set of data should satisfy WORM compliance by modifying the file access permissions for the set of data. In another example, if the data size for the set of data is greater than a threshold data size (e.g., is greater than 100 MB), then it may be determined that the set of data should be written to the WORM compliant hardware storage device; otherwise, if the data size for the set of data is not greater than the threshold data size, then it may be determined that the set of data should satisfy WORM compliance by modifying the file access permissions for the set of data. In another example, if an amount of available disk space remaining on the WORM compliant hardware storage device is less than the data size for the set of data, then it may be determined that the set of data should satisfy WORM compliance by modifying the file access permissions for the set of data. In another example, if it is detected that the storage cost for storing the set of data using the WORM compliant hardware storage devices is greater than a threshold cost, then it may be determined that the set of data should satisfy WORM compliance by modifying the file access permissions for the set of data (e.g., by setting the file access permissions to be read-only). If it is determined that the set of data should be stored using the WORM compliant hardware storage device, then step 511 is performed; otherwise if it is determined that the set of data should not be stored using the WORM compliant hardware storage device, then step 512 is performed.

In step 511, the set of data is written to the WORM compliant hardware storage device. In some cases, the set of data may have been stored using a non-WORM complaint data storage device, such as HDD 411 in FIG. 4A, within a data storage node and moved to a WORM compliant hardware storage device, such as the WORM compliant data storage 415 in FIG. 4A, within the data storage node. In step 513, the set of data is written to WORM compliant archival storage. The WORM compliant archival storage may comprise cloud-based archival storage. In one embodiment, upon detection that the set of data was written to the WORM compliant hardware storage device more than a threshold time ago (e.g., more than a week ago), the set of data may be written to the WORM compliant archival storage in order to maintain a secondary copy of the data to support disaster recovery. In step 512, the data access permissions for the set of data are modified to satisfy WORM compliance. In step 514, it is detected that the data access permissions for the set of data should be modified. In step 516, the data access permissions for the set of data are modified such that WORM compliance is no longer satisfied.

FIG. 5B is a flowchart describing another embodiment of a process for operating a data storage cluster. In one embodiment, the process of FIG. 5B may be performed by a storage appliance, such as storage appliance 170 or storage appliance 140 in FIG. 1A. The process of FIG. 5B may be performed by a data storage node, such as data storage node 404 in FIG. 4A or the integrated data management and storage system depicted in FIG. 4A that includes data storage node 404.

In step 532, it is detected that one or more files should be made WORM compliant. The one or more files may comprise files stored within one or more file directories. It may be detected that the one or more files should be made WORM compliance based on an SLA policy or upon receiving an instruction to lock the one or more files for a data retention time. In step 534, an amount of available disk space for a first WORM compliant storage device is identified. In step 536, a file size for the one or more files is identified. The file size for the one or more files may comprise the aggregate file size for the one or more files. In step 538, it is detected that the one or more files should be written to the first WORM compliant storage device based on the amount of available disk space and the file size. In one example, in response to detecting that the one or more files should be made WORM compliant and that the amount of available disk space is greater than the file size for the one or more files, the one or more files may be written to the first WORM compliant storage device.

In step 540, the one or more files are stored using the first WORM compliant storage device. In step 542, a number of reads of the one or more files within a threshold period of time is determined. In one example, the number of reads of the one or more files within the threshold period of time may comprise the number of reads for the one or more files within the last week or the last month. If the number of reads of the one or more files within the threshold period of time exceeds a threshold number of reads, then a copy of the one or more files may be stored using a second storage device that does not comprise a WORM compliant hardware storage device. In step 544, it is detected that a replicated version of the one or more files should be stored using the second storage device based on the number of reads of the one or more files within the threshold period of time. In step 546, the replicated version of the one or more files is stored using the second storage device. The second storage device may correspond with a non-WORM complaint data storage device, such as HDD 411 in FIG. 4A

One embodiment of the disclosed technology includes detecting that a set of data should be made immutable for a data retention time period, determining a data size for the set of data, determining a number of reads of the set of data within a past threshold time period, detecting that a first copy of the set of data should be stored using a WORM compliant hardware storage device based on the data size in response to detecting that the set of data should be made immutable for the data retention time period, storing the first copy of the set of data using the WORM compliant hardware storage device, detecting that a second copy of the set of data should be stored using a second storage device different from the WORM compliant hardware storage device based on the number of reads of the set of data within the past threshold time period, storing the second copy of the set of data using the second storage device, and modifying data access permissions for the second copy of the set of data stored on the second storage device such that the second copy of the set of data is read only.

One embodiment of the disclosed technology includes a memory configured to store one or more electronic files and one or more processors in communication with the memory. The one or more processors configured to detect that the one or more electronic files should be made immutable for a data retention time period and determine a data size for the one or more electronic files. The one or more processors configured to determine a number of reads of the one or more electronic files within a past threshold time period and detect that a first copy of the one or more electronic files should be stored using a WORM compliant hardware storage device based on the data size in response to detection that the one or more electronic files should be made immutable for the data retention time period. The one or more processors configured to cause the first copy of the one or more electronic files to be stored using the WORM compliant hardware storage device. The one or more processors configured to detect that a second copy of the one or more electronic files should be stored using a second storage device different from the WORM compliant hardware storage device based on the number of reads of the one or more electronic files within the past threshold time period and cause the second copy of the one or more electronic files to be stored using the second storage device. The one or more processors configured to modify data access permissions for the second copy of the one or more electronic files stored on the second storage device such that the second copy of the one or more electronic files is read only.

The disclosed technology may be described in the context of computer-executable instructions, such as software or program modules, being executed by a computer or processor. The computer-executable instructions may comprise portions of computer program code, routines, programs, objects, software components, data structures, or other types of computer-related structures that may be used to perform processes using a computer. In some cases, hardware or combinations of hardware and software may be substituted for software or used in place of software.

Computer program code used for implementing various operations or aspects of the disclosed technology may be developed using one or more programming languages, including an object oriented programming language such as Java or C++, a function programming language such as Scala, a procedural programming language such as the “C” programming language or Visual Basic, or a dynamic programming language such as Python or JavaScript. In some cases, computer program code or machine-level instructions derived from the computer program code may execute entirely on an end user's computer, partly on an end user's computer, partly on an end user's computer and partly on a remote computer, or entirely on a remote computer or server.

For purposes of this document, it should be noted that the dimensions of the various features depicted in the Figures may not necessarily be drawn to scale.

For purposes of this document, reference in the specification to “an embodiment,” “one embodiment,” “some embodiments,” or “another embodiment” may be used to describe different embodiments and do not necessarily refer to the same embodiment.

For purposes of this document, a connection may be a direct connection or an indirect connection (e.g., via another part). In some cases, when an element is referred to as being connected or coupled to another element, the element may be directly connected to the other element or indirectly connected to the other element via intervening elements. When an element is referred to as being directly connected to another element, then there are no intervening elements between the element and the other element.

For purposes of this document, the term “based on” may be read as “based at least in part on.”

For purposes of this document, without additional context, use of numerical terms such as a “first” object, a “second” object, and a “third” object may not imply an ordering of objects, but may instead be used for identification purposes to identify different objects.

For purposes of this document, the term “set” of objects may refer to a “set” of one or more of the objects.

Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims. 

What is claimed is:
 1. A method for operating a data management system, comprising: detecting that a set of data should be made immutable for a data retention time period; determining a data size for the set of data; determining a number of reads of the set of data within a past threshold time period; detecting that a first copy of the set of data should be stored using a WORM compliant hardware storage device that prevents alterations to data stored within the WORM compliant hardware storage device based on the data size in response to detecting that the set of data should be made immutable for the data retention time period; storing the first copy of the set of data using the WORM compliant hardware storage device; detecting that a second copy of the set of data should be stored using a second storage device different from the WORM compliant hardware storage device based on the number of reads of the set of data within the past threshold time period; storing the second copy of the set of data using the second storage device; and modifying data access permissions for the second copy of the set of data stored on the second storage device such that the second copy of the set of data is read only.
 2. The method of claim 1, wherein: the modifying the data access permissions for the second copy of the set of data stored on the second storage device includes modifying the data access permissions such that the second copy of the set of data cannot be altered.
 3. The method of claim 1, wherein: the detecting that the first copy of the set of data should be stored using the WORM compliant hardware storage device includes detecting that the data size is greater than a threshold data size.
 4. The method of claim 1, wherein: the detecting that the second copy of the set of data should be stored using the second storage device includes detecting that the number of reads of the set of data within the past threshold time period is greater than a threshold number of reads.
 5. The method of claim 1, further comprising: determining an amount of available disk space for the WORM compliant hardware storage device; and storing the first copy of the set of data using the WORM compliant hardware storage device in response to detecting that the data size for the set of data is less than the amount of available disk space for the WORM compliant hardware storage device.
 6. The method of claim 1, further comprising: determining a storage cost for storing the set of data using the WORM compliant hardware storage device based on the data size for the set of data and the data retention time period for the set of data; and storing the first copy of the set of data using the WORM compliant hardware storage device based on the storage cost for storing the set of data using the WORM compliant hardware storage device.
 7. The method of claim 1, further comprising: detecting that the data retention time period has elapsed; and modifying the data access permissions for the second copy of the set of data stored on the second storage device such that the second copy of the set of data is alterable in response to detecting that the data retention time period has elapsed.
 8. The method of claim 1, wherein: the WORM compliant hardware storage device is arranged within a first data storage node; and the second storage device is arranged within a second data storage node different from the first data storage node, the second data storage node is in communication with the first data storage node.
 9. The method of claim 1, wherein: the WORM compliant hardware storage device comprises a one-time programmable memory; and the second storage device comprises a hard disk drive.
 10. The method of claim 1, wherein: the set of data comprises a plurality of electronic files.
 11. A data management system, comprising: a memory configured to store one or more electronic files; and one or more processors in communication with the memory configured to detect that the one or more electronic files should be made immutable for a data retention time period and determine a data size for the one or more electronic files; the one or more processors configured to determine a number of reads of the one or more electronic files within a past threshold time period and detect that a first copy of the one or more electronic files should be stored using a WORM compliant hardware storage device based on the data size in response to detection that the one or more electronic files should be made immutable for the data retention time period, the one or more processors configured to cause the first copy of the one or more electronic files to be stored using the WORM compliant hardware storage device, the one or more processors configured to detect that a second copy of the one or more electronic files should be stored using a second storage device different from the WORM compliant hardware storage device based on the number of reads of the one or more electronic files within the past threshold time period and cause the second copy of the one or more electronic files to be stored using the second storage device, the one or more processors configured to modify data access permissions for the second copy of the one or more electronic files stored on the second storage device such that the second copy of the one or more electronic files is read only.
 12. The data management system of claim 11, wherein: the one or more processors configured to modify the data access permissions such that the second copy of the one or more electronic files cannot be altered.
 13. The data management system of claim 11, wherein: the one or more processors configured to detect that the first copy of the one or more electronic files should be stored using the WORM compliant hardware storage device if the data size is greater than a threshold data size.
 14. The data management system of claim 11, wherein: the one or more processors configured to detect that the second copy of the one or more electronic files should be stored using the second storage device if the number of reads of the one or more electronic files within the past threshold time period is greater than a threshold number of reads.
 15. The data management system of claim 11, wherein: the one or more processors configured to determine an amount of available disk space for the WORM compliant hardware storage device and store the first copy of the one or more electronic files using the WORM compliant hardware storage device in response to detection that the data size is less than the amount of available disk space for the WORM compliant hardware storage device.
 16. The data management system of claim 11, wherein: the one or more processors configured to determine a storage cost for storing the one or more electronic files using the WORM compliant hardware storage device based on the data size for the one or more electronic files and the data retention time period for the one or more electronic files, the one or more processors configured to store the first copy of the one or more electronic files using the WORM compliant hardware storage device based on the storage cost for storing the one or more electronic files using the WORM compliant hardware storage device.
 17. The data management system of claim 11, wherein: the second copy of the one or more electronic files comprises a replicated copy of the one or more electronic files.
 18. The data management system of claim 11, wherein: the one or more processors configured to detect that the data retention time period has elapsed and modify the data access permissions for the second copy of the one or more electronic files stored on the second storage device such that the second copy of the one or more electronic files is alterable in response to detection that the data retention time period has elapsed.
 19. The data management system of claim 11, wherein: the WORM compliant hardware storage device is arranged within a first data storage node; and the second storage device is arranged within a second data storage node different from the first data storage node, the second data storage node is in communication with the first data storage node.
 20. One or more storage devices containing processor readable code for programming one or more processors to perform a method for operating a data management system, the processor readable code comprising: processor readable code configured to detect that a set of data should be made immutable for a data retention time period and determine a data size for the set of data; processor readable code configured to determine a number of reads of the set of data within a past threshold time period; processor readable code configured to detect that a first copy of the set of data should be stored using a WORM compliant hardware storage device based on the data size in response to detection that the set of data should be made immutable for the data retention time period; processor readable code configured to store the first copy of the set of data using the WORM compliant hardware storage device; processor readable code configured to detect that a replicated version of the set of data should be stored using a second storage device different from the WORM compliant hardware storage device based on the number of reads of the set of data within the past threshold time period; processor readable code configured to store the replicated version of the set of data using the second storage device; and processor readable code configured to modify data access permissions for the replicated version of the set of data stored on the second storage device such that the replicated version of the set of data is read only. 